The field of this disclosure relates generally to systems and methods for item checkout, and more particularly, to checkout systems having a data reader capable of reading encoded data on a bottom surface of the item as the item passes through a read region of the data reader.
Data reading devices are used to read optical codes, acquire data, and capture a variety of images. Optical codes typically comprise a pattern of dark elements and light spaces. There are various types of optical codes, including one-dimensional codes, such as a Universal Product Code (“UPC”) and EAN/JAN codes, and stacked and two-dimensional codes, such as PDF417 and Maxicode codes.
Data reading devices are well known for reading UPC and other types of optical codes on packages, particularly in retail stores. Some data readers are installed at checkout stands or are built into a horizontal checkout counter so that a read region is projected through a transparent window to read the optical code on the package. In a fully automated system, a customer normally places items on a counter, a deck, or a conveyor and the items are conveyed by the conveyor or other means through the read region. In a semi-automatic system, a checkout clerk takes each item and moves it through the read region where the data reader captures the optical code.
One common data reader in such systems is an imaging reader that employs an imaging device or sensor array, such as a CCD (charge coupled device) imager or CMOS (complementary metal oxide semiconductor) imager. Imaging readers can be configured to read both 1-D and 2-D optical codes, as well as other types of optical codes or symbols and images of other items. Though some imaging readers are capable of using ambient light illumination, an imaging reader typically utilizes a light source to illuminate the item being read to provide the required signal response in the imaging device. An imager-based reader utilizes a camera or imager to generate electronic image data, typically in digital form, of an optical code. The image data is then processed to find and decode the optical code.
In one arrangement, the imaging reader may include one or more cameras operating in a linescan mode and configured to capture a series of single line views or scan lines of the optical code as the code crosses a read region. Multiple single line views of linescan mode may be combined to produce a raster image of the code, which is thereafter processed to decode the optical code. In another arrangement, the imaging reader may include one or more cameras operating in an area mode to capture a set of area views of the optical code as the code crosses the read region. The area views may thereafter be stitched together to produce a two-dimensional image that includes a complete image of the optical code. The image may thereafter be processed to decode the optical code.
In some embodiments of a checkout system, the read region for the imaging readers may be defined by a gap that separates two conveying elements (e.g., conveyor belts). In such embodiments, the imaging readers may be positioned beneath the conveying elements and positioned so that the field of view projects through the gap and allows the imaging readers to capture the optical code from the item as the item crosses the gap.
The present inventors have recognized certain limitations with present checkout systems. Certain checkout systems either cannot read or may have difficulty accurately capturing optical codes located on a conveyor-contacting, bottom surface of the item because the optical code is blocked from view. Consequently, a checkout clerk or customer has to remove the item from the conveyor and reposition it so that the optical code is not on the bottom surface. In some cases, manual processing of items may be necessary, which leads to inefficiencies such as increases in item processing time.
The present inventors have also recognized certain disadvantages associated with tunnel scanners that use imagers operating exclusively in either linescan mode or area mode to capture optical data on the bottom surface of the item. For instance, imagers operating in linescan mode require the item to move substantially uniformly across the read region to acquire a decodable image. Erratic motion or wobbling of the item as it crosses the read region may result in the data reader acquiring a distorted image of the optical code, which may prevent accurate decoding of the optical code. This issue with motion of the item is exacerbated in tunnel scanning systems where the read region is defined by a small gap separating two conveying elements, since items tend to wobble as they traverse the gap.
On the other hand, while imagers operating in an area mode usually have few issues handling erratic motion of items, such imagers have other disadvantages. For instance, area views typically require a large read region to ensure that a sufficiently large portion of the optical code is captured. However, in systems where the read region is defined by the width of the gap between conveying elements, it may be difficult to accommodate the larger read region while avoiding undesirable consequences. For instance, widening the gap to create a larger read region may lead to issues with items becoming lodged in or falling through the gap, or allowing dirt, dust, or other debris to interfere with the data readers.
The present inventors have, therefore, determined that it would be desirable to provide an improved imager-based reader and an improved tunnel or portal scanner system for automated checkout. Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.